1. Field of the Invention
The present general inventive concept relates to a method of determining alignment of a document for optical mark recognition (“OMR”), and more particularly to a method of determining alignment of a user-marked document for OMR using a non-fixed image capturing device. The present general inventive concept also relates a method of aligning a user-marked document for OMR using a non-fixed image capturing device, without requiring a de-skewing process.
2. Description of Related Art
Optical Mark Recognition (OMR) technology has been in use for decades. OMR is used to extract intended data from marked fields, such as check boxes and fill-in fields, on scanned forms or other documents. However, conventional OMR methods require that the scanner or camera be parallel to the document to be read.
Over the past few years, mobile device technology has significantly improved allowing for powerful smart phone devices with integrated digital cameras and various other devices. However, there exists a problem in accurately identifying marked areas on scanned forms or other documents when using a non-fixed image capture device, having a relatively low resolution.
That is, current OMR technology is limited to being only able to read pre-defined (i.e., fixed, parallel) positions relative to the scanned form, generally using a border or “broken ladder” marks around the form for alignment.
In order to identify the locations of the marks, prior techniques have manipulated the captured image, de-skewing the image in two dimensions prior to analyzing the page. However, this method only works well when the position of the camera and the page are both on the same plane, such as in the case of a desktop scanner or when using a fixed-position document camera.
FIG. 1 illustrates a perspective view of a conventional optical marker reader (“OMR”) system 10. The OMR system 10 includes a camera or scanning device 5 which is fixed relative to a document 25 to be read. In order to function, the conventional OMR systems 10 require that the camera or scanning device 5 be parallel to the document 25 since the system 10 cannot effectively compensate for varying document to camera angles.
Conventionally, identification of areas on the document has been done by first detecting a border around the document or a series of marks around the boundary of the page. In addition, a time-consuming de-skewing technique must also be applied in order for the conventional OMR technique to accurately identify and recognize marked fields. Typically, the de-skewing process reshapes an image of the document using its border, which is stretched and/or resized to match a predefined rectangular shape. Only then can the marks on the document be analyzed relative to that de-skewed page boundary.
However, the conventional OMR techniques are inadequate when applied using non-fixed capture devices, such as hand held cameras or mobile devices having a lower resolution, since the camera angles with respect to the document vary causing blurred captured images which can not be properly compensated for when analyzed for marked data fields. Conventional techniques are further complicated by lens distortion and general page curl.
Therefore, what is needed is an improved OMR technique which can accurately identify and analyze marked data fields using low resolution non-fixed cameras, without requiring a de-skewing process.